Research Projects

As many as 80% of autistic children experience sleep disruptions. Insufficient subjective sleep quality is associated with characteristics of autism, including repetitive behaviors, social and communication difficulties. However, the few objective sleep polysomnography (PSG) studies have not found significant effects. This likely reflects the small number of studies that utilized PSG as an objective sleep measure, small sample sizes, or assessment in a laboratory setting rather than in the child's home environment. 

Our own investigation of a larger sample using sleep PSG in autistic participants, in their home, found an increased slow-wave sleep (SWS) ratio in autistic children and adolescents and a lower rapid eye movement (REM) sleep ratio compared to typically developing (TD) counterparts. To address the critical question of whether dysregulated sleep is central to the development and characteristics of autism, we will test for differences in sleep fragmentation (actigraphy), sleep architecture (PSG) and daytime, awake, resting state electroencephalogram (EEG). We will examine if any observed sleep dysregulation is associated with the core symptoms, repetitive behaviors, and cognitive function of autistic individuals, or with dysregulated daytime, resting state EEG in autistic children and adolescents compared to TD counterparts.  

In collaboration with Project 2, we will examine if target engagement-induced normalization of sleep positively impacts autistic traits.  In collaboration with Project 3, we will examine if the hypothesized impairments in  sleep fragmentation, sleep architecture and daytime awake, resting state EEG in autistic individuals will be recapitulated in our animal experiments of sleep in genetic models of autism and if normalization of sleep fragmentation, sleep architecture and daytime awake, resting EEG in our animal models of autism will be associated with improved social communication and cognition, and reduced repetitive behaviors in these animal models. If we demonstrate that sleep fragmentation is responsible for the development of some autistic traits and sleep normalization alleviates them, we will have demonstrated the potential causality of autism and importance of sleep in autistic individuals.

In the current project, we propose to modulate the neurotransmitter systems implicated in the sleep-wake balance and examine their impact on sleep physiology in autistic children and adolescents. The goal is to promote better sleep by either targeting wakefulness by using receptors antagonists such as diphenhydramine (anti-histaminergic) and suvorexant (DORA) or promoting sleepiness by using a receptor agonist, zolpidem (nonbenzodiazepine receptor agonist).  

We aim at investigating the target engagement of three sleep-inducing agents with different mechanisms on gold standard PSG, actigraphy, and circadian rhythm in children and adolescents with autism between the ages of 8 and 17 years. The rationale behind the use of diphenhydramine, zolpidem, and suvorexant is related to their distinct pharmacological profiles and their differential effect on the primary neurotransmitters involved in sleep. Diphenhydramine has significant antihistaminic activities and concurrent sedative properties. Zolpidem is a nonbenzodiazepine receptor agonist and is a hypnotic targeting sleep-onset or sleep maintenance. Suvorexant is a DORA and is prescribed to target insomnia characterized by difficulty with sleep onset and/or sleep maintenance. Our pharmacological probing study of sleep architecture will allow us to examine, for the first time, whether we can effectively modulate altered sleep parameters in autistic children and adolescents and examine their impact on sleep quality and clinical features. 

Sleep is critical for proper synaptic connections and brain development. Our group previously established that sleep disruptions in zebrafish, like in other species, prevent normal structural synapse plasticity. Conversely, proper sleep and melatonin hypnotic/circadian treatment can improve these synaptic defects. While human (Projects 1 & 2) approaches permit exquisite studies of social interactions, repetitive behaviors, and associated cortical synaptic defects, zebrafish is a transparent vertebrate popular in developmental biology allowing whole brain and body investigation. 

Importantly, genes associated with autism like Fmr1, Shank3, and Cntnap2 are pan-neuronal, and their loss likely impacts the entire central nervous system during sleep. Using fluorescence-based polysomnography (fPSG) to capture whole-brain and whole-body imaging with single cell resolution during sleep, we have shown that zebrafish have sleep brain dynamics analogous to mammals. Similarities include a state we coined slow bursting sleep (SBS) which shares many commonalities with Non-REM slow wave sleep (SWS). Our preliminary data indicates that SBS is fragmented in developing Fmr1 zebrafish mutants. Further, studies from other groups have shown that based on actimetry, sleep/wake pattern is also disrupted in zebrafish cntnapt2ab and shank3ab mutants. However, their brain activity during sleep has not yet been investigated. 

In this project we will apply fPSG to these three genotypes (fmr1, shank3ab, and cntnap2ab mutants) and controls to fully characterize their sleep neural and muscular dynamics during development. Next, we will apply the same pharmacological interventions (H1R antihistamine, GABAA agonist, and hypocretin/orexin receptors antagonist) used in human (Project 2), to improve sleep onset latency and sleep/SBS consolidation in these autism risk gene mutants. Then, we will investigate the respective beneficial effects of these NREM/SWS/SBS-sleep interventions on structural synapse density using longitudinal imaging of telencephalic, hypothalamic and spinal cord circuits expressing synaptic proteins fused to fluorescent markers such as PSD95-eGFP, Synaptophysin-eGFP or Gephyrin-eGFP. The transparency of the zebrafish model will reveal how sleep dynamics are disrupted throughout the entire brain and how sleep interventions can also be beneficial for synaptic normalization throughout the CNS, further establishing the causal/aggravating role of disrupted sleep in the development of autistic traits.